Urological and nursing-related predictors of unplanned hospital readmission after percutaneous nephrolithotomy: A prospective cohort study

Abstract

BACKGROUND

Percutaneous nephrolithotomy (PNL) is the standard treatment for medium-sized and large kidney stones. Many potential complications of PNL may warrant hospital readmission (HR) after discharge, threatening patient safety and increasing the costs.

AIM

To estimate the rate of unplanned HR after PNL and identify its urological and nursing-related predictors.

METHODS

One hundred sixty-one patients were prospectively studied for HR after PNL from April 2022 to December 2022. The relevant urological and nursing-related characteristics of patients with and without unplanned HR after PNL were studied for association with HR, using univariate and multivariate analyses. Variables such as the demographic characteristics, comorbidities, laboratory and imaging characteristics, dietary status, operative time, number of kidney punctures, blood loss, urinary tract infections, and the receipt of instructions for catheter care and activities of daily living were included. A risk score was created.

RESULTS

The mean age of patients with HR (44.4 ± 12.7 years) and without HR (43.9 ± 12.6 years) was similar (P = 0.847). The overall stone-free rate was 88.8%. The total complication rate was 32.3% (52 patients), and the highest grade was IIIa, according to the modified Clavein grading system, resulting in an HR rate of 22.4%. History of preoperative pyuria (P = 0.001), hydronephrosis (P = 0.001) and mean stone size (P = 0.012), multiple renal punctures (P < 0.001), double J stent (P = 0.033), total operative time (P = 0.001), intraoperative injury (P = 0.011), postoperative urinary tract infection (P < 0.001), and inadequate instructions for urethral catheter (P = 0.001) and activity daily living (P = 0.048) were significantly associated with HR after PNL. On multivariate analysis, only preoperative pyuria (P = 0.004), intraoperative injury (P = 0.001), and inadequate instructions on urethral catheter care (P = 0.035) were associated with HR. The risk score of the independent predictors was 0-17; 0-4 (low risk), 5-9 (moderate risk), and 10-17 (high risk).

CONCLUSION

The rate of unplanned HR after PNL was relatively high (22.4%). The presence of pus cells in the preoperative urine analysis, intraoperative injury, and receiving inadequate instructions on urethral catheter care were independent predictors of HR after PNL. Combined studying of the urological and nursing-related predictors may promote the implementation of enhanced recovery protocols after PNL.

Key Words: Hospital readmission; Kidney stones; Percutaneous nephrolithotomy; Surgical complications; Stone clearance; Urinary catheter

Core Tip: Percutaneous nephrolithotomy (PNL) is the first line of treatment for large kidney stones. Although the complication rates are usually low, they may warrant hospital readmission (HR) in the convalescence course of patients undergoing PNL. The overall stone-free rate was 88.8%, and the total complication rate was 32.3%. The highest grade of complications was IIIa by the modified Clavein grading system, resulting in an HR rate of 22.4%. Several preoperative, operative, and postoperative variables may be associated with increased HR after PNL. However, only the preoperative pyuria, intraoperative injury, and inadequate instructions on urethral catheter care were independently associated with HR.

INTRODUCTION

Percutaneous nephrolithotomy (PNL) is the standard treatment for large kidney stones, measuring more than 2 cm, and lower pole stones greater than 1.5 cm[1,2]. It has many advantages and low complication rates. The latter may warrant hospital readmission (HR) in the convalescence course of patients undergoing PNL[3]. HR is commonly defined as an unscheduled readmission of a patient to a hospital within 30 days of discharge from the same or another hospital due to health problems relevant to the primary intervention[3,4]. HR is a professional and financial extra burden to the healthcare system, and it will be more costly on these axes if its frequency increases. Hence, reducing the risk factors of HR may help enhance its prevention, bringing its study into the focus of relevant research[4]. The study aimed to assess the rate of unplanned HR after PNL and identify its predictors. Many urological variables may influence the rate of unplanned HR, and they have been variably studied in the literature[3,5]. The preoperative variables include body mass index (BMI), stone size, presence of hydronephrosis, and comorbidities[3,6,7]. The operative variables include the operative time, intraoperative complications, and residual stones[8,9]. The postoperative variables include urinary tract infections (UTIs), placement of a double-J stent (JJ), and urinary obstruction[10-12]. Additionally, many nursing-related variables may be associated with PNL complications and HR. However, the literature lacks a comprehensive study of nursing-related variables[13,14]. Based on the intimate practical relevance between the urological and nursing-related variables, this study was designed to include both types of variables. We hypothesized that, in addition to the urological variables, nursing-related variables, such as nutritional status and diet, knowledge about the warning signs of complications, and instructions for catheter care and activities of daily living (ADLs), may have an impact on the HR after PNL.

MATERIALS AND METHODS

Study design

In a prospective cohort study, adult patients who underwent PNL in Assiut University Urology Hospital, Assiut, Egypt, between April 2022 and December 2022 for renal stones > 2 cm were studied for the rate of unplanned HR after PNL.

For a suitable sample size calculation, our hospital records, which showed a rate of 244 cases of PNL in 2021, and the sample size in a relevant previous study from our institute were considered[13]. Accordingly, a sample size of 150 patients was calculated using the equation of Steven K. Thompson: 95%CI, error ratio of 0.05, and a threshold of significance of 0.05. In addition, 15 patients (10% of the actual sample) were included to compensate for a potential percentage of lost-to-follow-up patients. The inclusion criteria were adult patients (> 18 years) with kidney stones > 2 cm in the largest dimension measured by a non-contrast computed tomography (NCCT) scan. The exclusion criteria included non-candidacy for anesthesia or PNL, failure or conversion of PNL to open surgery, refusal of PNL, and lost-to-follow-up patients.

Clinical workups

The evaluation of patients included meticulous history-taking, physical examination, and surgical fitness assessment. In addition, routine laboratory investigations were performed, including urinalysis, urine culture and sensitivity test, renal function tests, complete blood count, bleeding profiles, and a random blood sugar level. Imaging workups included abdominal ultrasonography (US), plain X-ray kidney-ureter-bladder (KUB), and multi-slice NCCT for all patients.

The surgical techniques and armamentarium of PNL were based on our classic technique, which was previously described[5]. On postoperative day one, KUB and US were performed. With the absence of residual stones, the nephrostomy tube (NT) was removed within the first postoperative day, and the ureteral catheter was removed on the second day. In the case of patients with JJ, they were scheduled for removal within 30–45 days after the operation. In the absence of fever, pain, or urine leakage, the patient was discharged on the third postoperative day. However, in the presence of residual fragments > 4 mm, a second look at PNL was performed at the same admission. The NCCT was done after three months to document the stone-free status in all patients. If there were urinary leakage, fever, or persistent renal colic, NCCT was performed at presentation as well. The auxiliary procedure was defined as any extra procedure of the same primary treatment modality or a different modality, such as ureteroscopy and JJ ureteral stents for treatment of residual stones > 4 mm or complications. During the first postoperative day, evaluation of the residual stones was performed before removal of the NT using US or KUB. Follow-up visits and imaging were planned for the diagnosis of the stone-free status by NCCT in cases with suspected residuals in the US or KUB.

Study outcomes

The primary outcome of the study was the rate of unplanned HR. It was defined as an admission to the hospital within 45 days of discharge from the same or another hospital due to health issues related to the PNL operation performed during the first admission without being scheduled in the primary treatment plan. The rationale for defining the upper limit of the time range of HR as 45 days after PNL was to cover the time range of JJ removal after PNL. At our institute, a significant proportion of our patients have JJ removal between 30 and 45 days after PNL.

Approval and registration

This study was approved by the local ethical committee at our institute, and the institutional review board approval number is 3750011/2022. In addition, this study was registered in the Clinical Trials registry (ID: NCT05852483). All procedures involving human participants adhered to the ethical standards of the Declaration of Helsinki and its amendments, or equivalent ethical standards. Informed consent was obtained from all participants in the study.

Statistical analysis

The data were analyzed using the Statistical Package for the Social Sciences, version 20.0 (SPSS Inc., Chicago, IL, United States). Qualitative (categorical) data (such as sex, age category, stone location, preoperative presence of pus cells or hydronephrosis, etc.) were presented in the form of frequency and percentage. However, quantitative (continuous) data (such as BMI, stone size, operative time, hospital stay, etc.) were presented as mean ± SD. Regarding the comparisons between the readmission and non-readmission groups, the χ² test was used for the qualitative data, and the independent t-test was used for the quantitative data. The skewness of the data was assessed with the Shapiro-Wilk test. Multivariate logistic regression analysis was used to define the predictors of unplanned HR. Multicollinearity of data was checked with the Belsley-Kuh-Welsch technique. A risk score was created for the independent predictors revealed from the multivariate analysis. The P value of < 0.05 was considered statistically significant.

RESULTS

Descriptive results

The current study included 161 patients, considering the proportion of patients lost to follow-up and the exclusion of ineligible patients (Figure 1). The age mean ± SD (range) was 44 ± 12.6 (20–65) years, female sex accounted for 39.8%, and the mean BMI ± SD was 24.4 ± 2.8 kg/m². Thirty-six patients (22.4%) had unplanned HR after PNL. The differences between these characteristics in groups of patients with (readmitted group) or without (non-readmitted group) HR were not statistically significant (Table 1).

Figure 1 Flowchart of patients who underwent percutaneous nephrolithotomy with or without unplanned hospital readmission. SWL: Extracorporeal shockwave lithotripsy; PNL: Percutaneous nephrolithotomy.

Table 1 Sociodemographic characteristics presented for total, readmitted, and non-readmitted patients (n = 161), n (%)/mean ± SD¹.

Sociodemographic variables	Total (n = 161)	Readmitted (n = 36)	Non-readmitted (n = 125)	P value
Sex
Male	97 (60.2)	25 (69.4)	72 (57.6)	0.138
Female	64 (39.8)	11 (30.6)	53 (42.4)
BMI
Underweight (< 18)	1 (0.6)	0 (0)	1 (0.8)	0.617
Normal weight (18-25)	101 (62.7)	24 (66.6)	77 (61.6)
Overweight (25-30)	47 (29.2)	11 (30.6)	36 (28.8)
Obese (> 30)	12 (7.5)	1 (2.8)	11 (8.8)
BMI	24.4 ± 2.8	24.1 ± 2.4	24.5 ± 2.9	0.430
Age group
From 20-39 years	63 (39.1)	17 (47.2)	46 (36.8)	0.091
From 40-59 years	78 (48.4)	12 (33.3)	66 (52.8)
From 60-65 years	20 (12.4)	7 (19.4)	13 (10.4)
Mean age (years)	44 ± 12.6	44.4 ± 12.7	43.9 ± 12.6	0.847
Marital status
Single	16 (9.9)	1 (2.8)	15 (12)	0.133
Married	141 (87.6)	35 (97.2)	106 (84.8)
Widow/widower	4 (2.5)	0 (0)	4 (3.2)
Occupation
Office work	37 (23)	7 (19.4)	30 (24)	0.372
Not working	124 (77)	29 (80.6)	95 (76)
Educational level
High	44 (27.3)	9 (25)	35 (28)	0.565
Secondary	33 (20.5)	9 (25)	24 (19.2)
Basic	30 (18.6)	5 (13.9)	25 (20)
Read and write	16 (10)	2 (5.5)	14 (11.2)
Illiterate	38 (23.6)	11 (30.6)	27 (21.6)
Residence
Urban	42 (26.1)	12 (33.3)	30 (24)	0.261
Rural	119 (73.9)	24 (66.7)	95 (76)
Special habits
Smoking	46 (28.6)	12 (33.3)	34 (27.2)	0.521
Use of excessive caffeine-containing beverages (café and tea)	66 (41)	16 (44.4)	50 (40)

¹χ² test used for qualitative data between the two groups and independent t-test used for quantitative data between the two groups.

BMI: Body mass index.

Postoperative infections (55.6%) were the commonest causes of HR, followed by urinary obstructions (13.9%) and hemorrhagic complications (11.1%). More than 80% of HRs occurred during the first 15 postoperative days. Most patients (88.9%) with HR had one HR, while 11.1% of them were readmitted twice. Most patients were treated conservatively, including antimicrobial therapy (83%). All the interventions were minimally invasive procedures: JJ or combined JJ and PCN were performed in 16.7% of patients. There was no mortality among all patients (Table 2).

Table 2 Causes, timing, duration, and management of hospital readmission in patients with complications (n = 36), n (%)/mean ± SD.

Variables
Frequency of readmission
Once	32 (88.9)
Twice	4 (11.1)
Causes of readmission
Inflammatory causes	20 (55.6)
Pyelonephritis	15 (41.7)
Other forms of UTIs	5 (13.9)
Hemorrhagic causes	4 (11.1)
Hematuria	2 (5.6)
Retroperitoneal hematoma	2 (5.6)
Combined inflammatory and hemorrhagic causes	4 (11.1)
Obstructive causes	5 (13.9)
Anuria	2 (5.6)
Acute urine retention	3 (8.3)
Extra urinary causes	3 (8.3)
Pulmonary complications	2 (5.6)
Gastric ulcers	1 (2.8)
Period from discharge to readmission
1-15 days after discharge	29 (80.6)
16-30 days after discharge	5 (13.9)
31-45 days after discharge	2 (5.6)
Mean length of hospital stay of readmission (day)	3.1 ± 2.8
Readmission management
Conservative treatment	30 (83.3)
Insertion of JJ	4 (11.1)
Insertion of both JJ and nephrostomy tube	2 (5.6)

UTI: Urinary tract infections; JJ: Double-J stent.

The final SFR was 88.8% after 3 months postoperatively. Treatment of residual stones by extracorporeal shock wave lithotripsy was performed in 8 patients (5%). However, no surgical interventions were carried out for residual stones; spontaneous passage occurred in 4 patients (2.5%), and dissolution therapy was used in 6 patients (3.7%).

Comparative results

In the comparison of preoperative clinical characteristics (Table 3), readmitted patients showed a significantly higher incidence of pus cells in the preoperative urine analysis (P = 0.001), larger mean stone size (P = 0.012), and more preoperative hydronephrosis (P = 0.001).

Table 3 Comparison of the preoperative clinical variables between the readmitted and non-readmitted groups of patients (n = 161), n (%)/mean ± SD.

Variables	Readmitted (n = 36)	Non-readmitted (n = 125)	P value
Comorbidities
Hypertension	5 (13.9)	19 (15.2)	0.542
Diabetes mellitus	2 (5.6)	9 (7.2)	0.537
Chronic kidney disease	1 (2.8)	3 (2.4)	0.641
Nutrition and fluid assessment
Normal diet	27 (75)	100 (80)	0.331
Specific diet (diabetic, salt-free)	9 (25)	25 (20)
Average fluid intake (2-3 L/day)	28 (77.8)	102 (81.6)	0.383
Fluid intake > 3 L/day	8 (22.2)	23 (18.4)
Previous urological procedures
Endourologic surgery	4 (11.1)	23 (18.4)	0.222
Open surgery	13 (36.1)	36 (28.8)	0.260
ESWL	2 (5.6)	9 (7.2)	0.537
Laboratory investigations
Pus cells in urine analysis	29 (80.6)	58 (46.4)	0.001
Mean serum creatinine (mg/dL)	1.24 ± 0.8	1.12 ± 0.6	0.321
Mean hemoglobin level (g/dL)	13.14 ± 2.3	12.9 ± 2.2	0.557
Mean prothrombin time (second)	12.4 ± 0.8	12.2 ± 0.7	0.095
Preoperative findings in computed tomography
Mean stone size (cm)	2.64 ± 0.71	2.31 ± 0.68	0.012
Solitary kidney	4 (11.1)	5 (4)	0.114
Stone location
Right kidney	22 (61.1)	55 (44)	0.052
Left kidney	14 (38.9)	70 (56)
Preoperative hydronephrosis	26 (72.2)	48 (38.4)	0.001
Presence of preoperative JJ	8 (22.2)	23 (18.4)	0.383

¹χ² test used for qualitative data between the two groups and independent t-test used for quantitative data between the two groups.

ESWL: Extracorporeal shockwave lithotripsy; JJ: Double-J stent.

Regarding the operative findings (Table 4), the readmitted patients exhibited significantly higher rates of multiple renal punctures (P < 0.001), longer mean total (P = 0.001) and procedural (P < 0.001) operative times, and a higher rate of JJ insertion (P = 0.033). The differences in indication (P = 0.082) and duration (P = 0.062) of JJ insertion did not reach statistical significance between the two groups (Table 4).

Table 4 Comparison of the operative and postoperative variables between the readmitted and non-readmitted groups of patients (n = 161), n (%)/mean ± SD.

Variables	Readmitted (n = 36)	Non-readmitted (n = 125)	P value1
Operative variables
Approach
Infracostal	31 (86.1)	112 (89.6)	0.555
Supracostal	5 (13.9)	13 (10.4)
Number of punctures
Single	6 (16.7)	63 (50.40	< 0.001
Multiples	30 (83.3)	62 (49.6)
Target calyx of puncture
Upper calyx	4 (11.1)	12 (9.6)	0.671
Middle calyx	9 (25)	41 (32.8)
Lower calyx	23 (63.9)	72 (57.6)
Type of disintegrators
Ultrasonic	2 (5.6)	4 (3.2)	0.403
Pneumatic	34 (94.4)	121 (96.8)
Academic qualification of the main operator
Professor	16 (44.4)	51 (40.8)	0.665
Assistant professor	0 (0)	2 (1.6)
Lecturer	19 (52.8)	63 (50.4)
Assistant lecturer	1 (2.8)	9 (7.2)
Patient position
Supine	2 (5.6)	20 (16)	0.167
Prone	34 (94.4)	105 (84)
Operative time
Total operation time (minute)	182.5 ± 34.7	150.72 ± 31.3	0.001
PNL procedural time (minute)	158 ± 27.3	130 ± 29	< 0.001
Ureteral JJ
Number of patients	12 (33.3)	21 (16.8)	0.033
Duration	43.3 ± 19	59.6 ± 25.5	0.062
Indications
For residual stone	10 (27.8)	16 (12.8)	0.082
For other causes	2 (5.6)	5 (4)
Nephrostomy tube
Number of patients	33 (82.4)	103 (82.4)	0.136
Removal before discharge	33 (91.7)	92 (73.6)	0.146
Removal after discharge (within 3 days)	1 (2.8)	10 (8)
Postoperative Variables
UOP at the 1st postoperative 24 hours (mL)	925 ± 210.95	956.80 ± 267.48	0.512
Pain degree
No pain	20 (55.6)	75 (60)	0.172
Mild	1 (2.8)	15 (12)
Moderate	8 (22.2)	23 (18.4)
Sever	7 (19.4)	12 (9.6)
Discharge with urethral catheter and its duration (day)
Discharge with urinary catheter	24 (66.7)	54 (43.2)	0.011
2-7	18 (50)	85 (68)	0.014
8-13	10 (27.8)	32 (25.6)
14-20	8 (22.2)	8 (6.4)
Mean duration with catheter	9.5 ± 6	6.4 ± 3.7	< 0.001
Complications
Pneumothorax	5 (13.9)	7 (5.6)	0.100
Intraperitoneal fluid collection	10 (27.8)	6 (4.8)	< 0.001
Postoperative urinary tract infection	13 (36.1)	20 (16)	0.011
Received pre-discharge instructions
Instructions about wound care	16 (44.4)	70 (56)	0.150
Instructions about medications	25 (69.4)	81 (64.8)	0.379
Activity daily living instructions	12 (33.3)	65 (52)	0.048
Instructions about urethral catheter care	7 (19.4)	55 (44)	0.005
Diet instructions	8 (22.2)	27 (21.6)	0.550
Follow-up appointment	19 (68.2)	63 (50.4)	0.475
Education on warning signs	18 (50)	57 (45.6)	0.390
Hospital stay (day)	5.1 ± 3.8	4.6 ± 2.9	0.370

¹χ² test used for qualitative data between the two groups and independent t-test used for quantitative data between the two groups.

JJ: Double-J stent; UOP: Urine output; PNL: Percutaneous nephrolithotomy.

In the comparison of the postoperative characteristics (Table 4), the readmitted group had significantly higher rates of discharge with urethral catheter (P = 0.011), longer duration of urethral catheter (P < 0.001), intraperitoneal fluid collection (P < 0.001), UTIs (P = 0.011), and inadequate instructions for care of urethral catheter (P = 0.005) and ADLs (P = 0.048).

For all patients, the minimum follow-up duration was 45 days. The modified Clavien-Dindo system was used to grade complications, based on the modality of treatment (Table 5).

Table 5 Postoperative complications and their grades and management (n = 52).

Complications	Frequency	Number of readmitted patients	Treatment regimen (number of patients)	Modified Clavein grade
Obstructive complications
Anuria	2	2	JJ placement (2)	IIIa
Acute urinary retention	3	3	Urethral catheterization (3)	II
Renal pain/colic	8	0	Medical expulsive (8). Antimicrobial therapy (3)	II, II
Genitourinary infections
Acute pyelonephritis	18	15	JJ placement (4) with percutaneous nephrostomy (2). Antimicrobial therapy (18)	IIIa, II
Other infection1	5	5	Antimicrobial therapy	II
Hemorrhagic complications
Gross hematuria	5	2	Blood transfusion, intravenous fluids, and anti-bleeding measures (2). Antibleeding measures only (3)	II, II
Retroperitoneal hematoma	3	2	Blood transfusion (1). Antimicrobial/antibleeding therapy (3)	II
Combined infections and hemorrhage	4	4	Blood transfusion (1). Antimicrobial therapy (4). Angioembolization (1)	II, II, IIIa
Extraurologic
Pneumonia	3	2	Antimicrobial therapy (3)	II
Peptic ulcer	1	1	Upper GIT endoscopy and medical therapy	IIIa
Total	52	36		42 II and 10 IIIa

¹They included infected perinephric collections in three cases and combined acute epididymo-orchitis with gross pyuria in two cases. Six cases of infected, neglected gauze or encrustations at the nephrostomy tube site were not included here; they required no treatment other than local cleansing.

GIT: Gastrointestinal tract, JJ: Double-J stent.

Multivariate analysis

In multivariate logistic regression, the presence of pus cells in preoperative urine analysis (P = 0.004), intraoperative injuries (P = 0.001), and inadequate nursing instructions for urethral catheter care (P = 0.035) were the independent predictors of unplanned HR after PNL. However, the operative time (P = 0.084), intraoperative insertion of JJ (P = 0.060), and discharge with a urethral catheter (P = 0.076) did not show statistical significance (Table 6).

Table 6 Multivariate logistic regression analysis of the predictors of post-percutaneous nephrolithotomy hospital readmission.

Potential predictors	OR	95%CI	P value
Preoperative predictors
Positive pus cells in urine analysis	5.8	(1.7-19.5)	0.004
Stone size	0.6	(0.23-1.5)	0.282
Preoperative hydronephrosis	1.43	(0.41-5)	0.575
Intraoperative predictors
Total operation time (minute)	1	(0.92-1.04)	0.434
PNL procedural time (minute)	1.1	(1-1.15)	0.084
Multiple renal punctures	2.9	(0.8-10.8)	0.103
Insertion of a double-J stent	0.25	(0.06-1.1)	0.060
Occurrence of intraoperative injuries	15	(3-75)	0.001
Postoperative predictors
Postoperative urinary tract infections	0.58	(0.43-9.91)	0.554
Discharge with urethral catheter	1.1	(1-1.3)	0.076
Duration of urethral catheterization	1.13	(1-1.3)	0.110
Inadequate activity daily living instructions	0.12	(0.14-1.26)	0.123
Inadequate urethral catheter care instructions	0.25	(0.08-0.9)	0.035

PNL: Percutaneous nephrolithotomy.

A clinical risk score was developed for the independent predictors identified by the multivariate regression model by converting the β-coefficients [ln(OR)] into integer scores (Figure 2). The total score ranges from 0 to 17, with higher scores indicating a greater risk of unplanned HR. Patients can be stratified into low (0–4), moderate (5–9), and high-risk (10–17) groups (Table 7).

Figure 2 A chart representing the risk score of the independent predictors of unplanned hospital readmission after percutaneous nephrolithotomy. HR: Hospital readmission.

Table 7 Risk score for the independent predictors based on the multivariate logistic regression.

Item	Risk score
Predictors
Positive pus cell in preoperative urine analysis	5
Intraperitoneal injuries	8
Inadequate catheter care instructions	4
Total score	17
Categorized score
Low risk	0–4
Moderate risk	5–9
High risk	10–17

DISCUSSION

PNL is the first-line treatment for large kidney stones, and it is regarded as a safe method[1]. The major complications associated with PNL are generally related to the intraoperative injuries of neighboring organs, postoperative bleeding, and UTIs. Unplanned HR may occur in the postoperative period due to unpredictable complications[3].

In the present study, the mean age of patients was 44 ± 12.6 years. Similarly, in a study by Tepeler et al[6], the mean age of the patients was 46.6 ± 13.2 years. Also, Keskin et al[7] reported a similar mean age of 42.1 ± 14.3 years[7].

In the current study, the mean BMI was 24 ± 2.8 kg/m². This finding aligns with the findings of previous studies[6,15]. The current results showed that most patients had a normal BMI. This finding was consistent with earlier research, which referred to that the majority of patients with kidney stones also have a normal BMI[16].

The complication rate of PNL has improved from 75% in its early years to 30% in the current literature[17,18]. Similarly, the current study showed a postoperative complication rate of 32.3%. In the literature, the rates of unplanned HR after PNL range from 1.7% to 27.1%[6,7,19-21]. In our study, the rate of HR was 22.4%, which was consistent with the literature from countries with similar characteristics[7].

The rate of preoperative hydronephrosis in the readmitted patients was higher than that in the non-readmitted patients. This finding was in agreement with the results of a study by Danacıoğlu et al[3] who stated preoperative hydronephrosis as a risk factor for HR. However, in the current multivariate analysis, it was not a significant factor. The presence of hydronephrosis may be considered an advantage for creating access to the kidney. Still, however, it might be a disadvantage during stone disintegration due to the potential mobilization within the dilated kidneys. Consequently, hydronephrosis might influence the operative time and success rates of PNL procedures. Accordingly, surgeries performed with a smaller stone burden, before hydronephrosis development, may have a significant effect on HR rates[22].

The current results revealed that the presence of pus cells in the preoperative urine analysis was significantly higher in the readmitted patients than in the non-readmitted patients. This finding was similar to the results of the study by Danacıoğlu et al[3], who reported a significant difference between readmitted and non-readmitted patients in preoperative urine culture positivity. Also, they found significant associations between the preoperative positive urine cultures and sepsis after PNL[3].

The current study revealed a significant difference between readmitted and non-readmitted patients in the size of stones. This finding was similar to previous results. This can be explained by both the longer duration of the operation and the higher rates of residual stones or fragments[7]. In addition, if surgery is planned when patients are asymptomatic and the stone burden is not high, it may be possible to decrease the HR rate. Complex and large stones may require multiple access tracts and more maneuvers during operation to access various calyces, increasing the bleeding potential[8]. The large size of stones in previous studies resulted in prolonged operation time, a higher number of punctures, intraperitoneal injuries, and larger residual stones. The shortest median operative time was associated with the small sizes of stones. However, the medium-sized stones required a shorter operative time when compared to the large ones[23].

The current study showed that multiple punctures were significant predictors of HR. This finding was in agreement with previous results, where the upper pole access or multiple accesses were more likely associated with HR after PNL surgery[9]. Also, multiple renal accesses are usually required to manage complex and large stones within the complex pelvicalyceal systems. Multiple renal punctures and accesses increase the risk of parenchymal vascular injuries, thus increasing the risk of hemorrhage[8].

The present study revealed that JJ was a predictor of patient HR. This finding was in agreement with the results by Tomer et al[10], who showed that JJ placement was a significant risk factor for HR for PNL patients. Also, they reported that encrustation is a common phenomenon that can occur with the placement of JJ into the urinary tract, and it can lead to serious complications[10]. It has been reported that JJs act as foreign bodies and may cause UTIs, including pyonephrosis, that may lead to nonfunctioning kidneys. Therefore, JJ should be removed as early as possible after it serves its purpose or changed frequently to reduce related complications and morbidity[11].

The present results revealed that a large proportion of patients required NT post-PLN. This finding was consistent with Chang et al[24], who stated that the purpose of NT was kidney drainage to enhance hemostasis and healing of the access tract, prevent extravasation of urine, and provide access to the kidney for any auxiliary procedures. In addition, NT may be necessary for potential residual stones, which increase the risk of postoperative infections[24].

The current study demonstrated that postoperative UTIs were predictors of HR. This finding was in line with the results of a study by Khaleel and Farhan[12], who found that PNL was associated with postoperative fever and sepsis[12]. Also, Sharma et al[25] added that severe preoperative hydronephrosis, a higher number of punctures, and a longer duration of surgery were found to be significant factors associated with postoperative complications.

The current study revealed statistically significant differences between readmitted and non-readmitted patients, considering the mean duration of urethral catheterization. The duration of urethral catheter use was an important risk factor for post-PNL complications. Shorter durations of urethral catheterization had fewer adverse effects on patients compared to longer durations. Short catheterization was defined as inserting a urethral catheter for less than 7 days. Therefore, short-term urethral catheterization may help reduce complications, including sepsis, catheter obstruction, and HR. Additionally, UTIs significantly affect patients with indwelling urethral catheters[26].

The current results showed that predischarge instructions for catheter care were risk factors for HR. Following basic infection control measures is a crucial duty for nurses to ensure proper urinary catheter care. Additionally, nurses should educate patients on the correct positioning of the catheter and drainage bag. These instructions help prevent ascending infections by promoting proper drainage and avoiding urine stagnation. It was reported that patients who receive proper education have an improved understanding of discharge instructions and a lower risk of HR[27,28].

Additionally, the present study showed a significant effect of pre-discharge instructions regarding ADLs on HR. Murray et al[29] defined ADLs as the essential skills required to independently care for oneself, including diet, bathing, and mobility. Furthermore, it was noted that ADLs have predictive value for HR and mortality in various conditions. Patients with impaired baseline physical functions are much more likely to experience HR within 30 days of hospital discharge[29].

Effective nursing interventions can greatly reduce HR after PNL. By emphasizing patient education, discharge planning, and post-discharge support, nurses can empower patients to manage their recovery, recognize potential complications, and avoid unnecessary HRs. Nurses play a vital role in educating patients to recognize early signs of complications such as infections, bleeding, and urinary obstruction. Prompt intervention can prevent the need for HR. Specific nursing interventions include medication recognition, catheter care, dietary instructions, education on ADLs, and teaching recognition of complications. These findings support the recommendations for a combined study of the urological and nursing-related predictors of HR after PNL[13,14].

The current study revealed a rate of HR after PNL of 22.4%. This finding was similar to the rate (27.1%) reported by Keskin et al[7], who attributed this high HR rate to major complications after PNL, such as infections, hemorrhage, and intraperitoneal injury[7]. However, Beiko et al[21] and Tepeler et al[6] reported lower HR rates after PNL (4%–15%)[6,21]. This difference in HR rates between our results and those of previous studies might further be attributed to the different definitions of HR and its duration.

The current results revealed that more than half (55.6%) of HRs were due to UTIs. This finding was in agreement with the results by Babich et al[30], who reported that 57.1% of readmitted patients had infections. The recurrent UTI was the most common cause[30]. Similarly, Kumar et al[20] reported that the most common cause of HR was urosepsis[20]. Keskin et al[7] mentioned that 9.6% of readmitted patients had post-PLN sepsis.

The current study reported that 11.1% of HRs were due to hemorrhagic causes. This finding was in line with the results of Keskin et al[7] and Beiko et al[21], who reported that 8.3% of HRs were due to hemorrhagic causes.

The current study revealed that about 8.3% of HRs were due to obstructive complications. This finding was in line with a study by Armitage et al[19]. Additionally, they reported that the acute urinary retention incidence was 0.5%. However, our study revealed that 5.6% of HRs were due to anuria, which was similar to previous results from our country[31].

The Clavien grading system has recently been used to evaluate the complications of PNL, and the grades are commonly low[15,17]. Similarly, the current results showed that the highest grade was IIIa, warranting minimally invasive interventions.

The combination of urological and nursing-related variables was a cardinal characteristic in the differences of the current study from most studies in the relevant literature[3,6,7,30]. While the similarities of the results were correlated to most variables, the natures of the predictors of HR after PNL have been remarkably varied per individual study[3,6,7,9-11,23]. This variation can be attributed to methodological differences among studies, such as the sample size, epidemiological study design, and definition of the variables[3,6,9,19,20]. Additionally, the technical differences in PNL procedures and armamentarium were considerable[7,21,22].

This study has the advantage of presenting the experience of studying the risk factors of HR after PNL in one of the developing countries with a high incidence of urolithiasis[5,31]. In addition, it addressed both the urological and healthcare risk factors for this significant topic in urolithiasis and endourology. Hence, this study design promotes the implementation of a recent protocol for perioperative patient care and management known as enhanced recovery after surgery. This protocol comprises domains for health education, nutrition assessment and intervention, postoperative fluid management, postoperative multimodal pain control, early postoperative mobilization, and early removal of indwelling urinary catheters or tubes. It requires multidisciplinary efforts of nurses, clinicians, anesthesiologists, and physical therapists[14].

The limitations of this study included the inability to address the rates of HR in subclasses of patients, such as the age groups, stone size categories, and types of intraoperative complications. In addition, the generalizability of the current results is limited by the single-center nature of the study.

Studies with large probability samples in different geographical regions are recommended to explore the main aspects of unplanned HR and maximize the benefits of combined studying of urological and nursing-related predictors of unplanned HR after PNL. In addition, practical training of both nurses and physicians should consider the significance of awareness of aspects of the other specialty on the patient outcomes after PNL.

CONCLUSION

Despite the high SFR, the unplanned HR rate after PNL was relatively high. The positive pus cells in preoperative urine analysis, large stone size, presence of preoperative hydronephrosis, number of renal punctures, intraoperative insertion of JJ, intraperitoneal injury, duration of urethral cauterization, postoperative UTIs, and inadequate instructions about urethral catheter care and ADLs were associated with an increased rate of HR. However, the independent predictors of HR after PNL were pus cells in preoperative urine analysis, intraperitoneal injuries, and inadequate instructions on urethral catheter care. The novel combined study of both the urological and nursing-related predictors in the current study revealed their significant effects on the unplanned HR after NL. The emphasis on this combination and its potential impact can enhance the practical performance of the medical teams and improve the clinical outcomes of kidney stone management by PNL, particularly in developing countries.